/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_lattice_q31.c
*
* Description:	Q31 FIR lattice filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_Lattice
 * @{
 */


/**
 * @brief Processing function for the Q31 FIR lattice filter.
 * @param[in]  *S        points to an instance of the Q31 FIR lattice structure.
 * @param[in]  *pSrc     points to the block of input data.
 * @param[out] *pDst     points to the block of output data
 * @param[in]  blockSize number of samples to process.
 * @return none.
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 * In order to avoid overflows the input signal must be scaled down by 2*log2(numStages) bits.
 */

#ifndef ARM_MATH_CM0_FAMILY

/* Run the below code for Cortex-M4 and Cortex-M3 */

void arm_fir_lattice_q31(
    const arm_fir_lattice_instance_q31 *S,
    q31_t *pSrc,
    q31_t *pDst,
    uint32_t blockSize)
{
    q31_t *pState;                                 /* State pointer */
    q31_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    q31_t *px;                                     /* temporary state pointer */
    q31_t *pk;                                     /* temporary coefficient pointer */
    q31_t fcurr1, fnext1, gcurr1 = 0, gnext1;      /* temporary variables for first sample in loop unrolling */
    q31_t fcurr2, fnext2, gnext2;                  /* temporary variables for second sample in loop unrolling */
    uint32_t numStages = S->numStages;             /* Length of the filter */
    uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */
    q31_t k;

    pState = &S->pState[0];

    blkCnt = blockSize >> 1u;

    /* First part of the processing with loop unrolling.  Compute 2 outputs at a time.
       a second loop below computes the remaining 1 sample. */
    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurr1 = *pSrc++;

        /* f0(n) = x(n) */
        fcurr2 = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* read g0(n - 1) from state buffer */
        gcurr1 = *px;

        /* Read the reflection coefficient */
        k = *pk++;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);

        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
        fnext1 = fcurr1 + (fnext1 << 1u);
        gnext1 = gcurr1 + (gnext1 << 1u);

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext2 = (q31_t) (((q63_t) fcurr1 * k) >> 32);

        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32);
        fnext2 = fcurr2 + (fnext2 << 1u);
        gnext2 = fcurr1 + (gnext2 << 1u);

        /* save g1(n) in state buffer */
        *px++ = fcurr2;

        /* f1(n) is saved in fcurr1
           for next stage processing */
        fcurr1 = fnext1;
        fcurr2 = fnext2;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {

            /* Read the reflection coefficient */
            k = *pk++;

            /* read g2(n) from state buffer */
            gcurr1 = *px;

            /* save g1(n) in state buffer */
            *px++ = gnext2;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
            fnext2 = (q31_t) (((q63_t) gnext1 * k) >> 32);

            fnext1 = fcurr1 + (fnext1 << 1u);
            fnext2 = fcurr2 + (fnext2 << 1u);

            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32);
            gnext2 = gnext1 + (gnext2 << 1u);

            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
            gnext1 = gcurr1 + (gnext1 << 1u);

            /* f1(n) is saved in fcurr1
               for next stage processing */
            fcurr1 = fnext1;
            fcurr2 = fnext2;

            stageCnt--;

        }

        /* y(n) = fN(n) */
        *pDst++ = fcurr1;
        *pDst++ = fcurr2;

        blkCnt--;

    }

    /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
     ** No loop unrolling is used. */
    blkCnt = blockSize % 0x2u;

    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurr1 = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* read g0(n - 1) from state buffer */
        gcurr1 = *px;

        /* Read the reflection coefficient */
        k = *pk++;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
        fnext1 = fcurr1 + (fnext1 << 1u);

        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
        gnext1 = gcurr1 + (gnext1 << 1u);

        /* save g1(n) in state buffer */
        *px++ = fcurr1;

        /* f1(n) is saved in fcurr1
           for next stage processing */
        fcurr1 = fnext1;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {
            /* Read the reflection coefficient */
            k = *pk++;

            /* read g2(n) from state buffer */
            gcurr1 = *px;

            /* save g1(n) in state buffer */
            *px++ = gnext1;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
            fnext1 = fcurr1 + (fnext1 << 1u);

            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
            gnext1 = gcurr1 + (gnext1 << 1u);

            /* f1(n) is saved in fcurr1
               for next stage processing */
            fcurr1 = fnext1;

            stageCnt--;

        }


        /* y(n) = fN(n) */
        *pDst++ = fcurr1;

        blkCnt--;

    }


}


#else

/* Run the below code for Cortex-M0 */

void arm_fir_lattice_q31(
    const arm_fir_lattice_instance_q31 *S,
    q31_t *pSrc,
    q31_t *pDst,
    uint32_t blockSize)
{
    q31_t *pState;                                 /* State pointer */
    q31_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    q31_t *px;                                     /* temporary state pointer */
    q31_t *pk;                                     /* temporary coefficient pointer */
    q31_t fcurr, fnext, gcurr, gnext;              /* temporary variables */
    uint32_t numStages = S->numStages;             /* Length of the filter */
    uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

    pState = &S->pState[0];

    blkCnt = blockSize;

    while(blkCnt > 0u)
    {
        /* f0(n) = x(n) */
        fcurr = *pSrc++;

        /* Initialize coeff pointer */
        pk = (pCoeffs);

        /* Initialize state pointer */
        px = pState;

        /* read g0(n-1) from state buffer */
        gcurr = *px;

        /* for sample 1 processing */
        /* f1(n) = f0(n) +  K1 * g0(n-1) */
        fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr;
        /* g1(n) = f0(n) * K1  +  g0(n-1) */
        gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr;
        /* save g1(n) in state buffer */
        *px++ = fcurr;

        /* f1(n) is saved in fcurr1
           for next stage processing */
        fcurr = fnext;

        stageCnt = (numStages - 1u);

        /* stage loop */
        while(stageCnt > 0u)
        {
            /* read g2(n) from state buffer */
            gcurr = *px;

            /* save g1(n) in state buffer */
            *px++ = gnext;

            /* Sample processing for K2, K3.... */
            /* f2(n) = f1(n) +  K2 * g1(n-1) */
            fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr;
            /* g2(n) = f1(n) * K2  +  g1(n-1) */
            gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr;

            /* f1(n) is saved in fcurr1
               for next stage processing */
            fcurr = fnext;

            stageCnt--;

        }

        /* y(n) = fN(n) */
        *pDst++ = fcurr;

        blkCnt--;

    }

}

#endif /*   #ifndef ARM_MATH_CM0_FAMILY */


/**
 * @} end of FIR_Lattice group
 */
